In a perfect world a list of email addresses could be verified with only two outcomes. Valid or Invalid. You could simply keep the good and delete the bad.

However, the reality is that all email servers are not created equal and a complete confirmation of deliverability is not possible with some domains which give us the Accept All and Unknown results. What we can do is verify the status of each email address to help you decide how to manage your list. Consider these points in evaluating the risks involved in sending to Unknown or Accept All emails.

#1: How were the emails collected? If they are all opt-in emails from people who signed up for your communications then they are likely to be good addresses. If the list was purchased or inherited from another source then the performance of Accept All or Unknown emails is likely going to be weak and your sender reputation may suffer.

#2: How old is the contact? Most Accept All addresses are business domains. They are people's work email. If someone gave you their work email 4 years ago, they may no longer be employed there. The email won't be opened or read by anyone. Even worse, it could bounce if the email address no longer exists.

If you're confident in the way the contacts were collected, and the age of the data is relatively new then you may consider mailing to the Unknown and Accept All results. Just be aware that these emails may not match the performance of the emails verified as Valid.